In the marine industry, the selection of marine cranes is numerous. It seems that various kinds of offshore cranes have their respective designs and uses. So, what production standards a qualified crane on ships should possess in the design is the crucial point for us to choose them.
What Is A Marine Crane?
Marine cranes are a kind of lifting device installed on marine decks or working platforms. They are specially designed for loading and unloading cargo, lifting facilities, and emergency rescues on the sea. That also means that choosing a qualified boat crane adapting to the standards can enhance work efficiency and reduce product waste and replacement.
Metal Materials and Selection Reasons of Marine Crane
Steel: It has excellent mechanical properties and can bear the huge load and stress generated by the crane on ships during operation. They are easy to weld, cut and shape, and easy to manufacture and install. The cost is relatively low, and the supply is sufficient, which is suitable for mass production. Although its corrosion resistance is poor, its service life in the marine environment can be significantly improved through anti-corrosion treatments such as painting and zinc plating.
Aluminum alloy: Low density of aluminum alloy can reduce the dead weight of the boat crane, improve the effective load capacity, and reduce energy consumption. After special heat treatment, the strength of aluminum alloy approaches or even exceeds that of high-quality steel. Good plasticity can be maintained. Their surfaces are easy to form dense oxide films and have good resistance to corrosive media such as seawater.
The Complete and Qualified Design Standards of Marine Crane
Performance Design Standards
Lifting capacity: Rated lifting capacity is the key index, and the lifting capacity under different working radii should be clearly defined. The lifting height is also strictly required, and the vertical distance from the marine crane base to the highest position of the hook is generally not less than 15m.
Working speed: The lifting speed varies according to the lifting weight, usually the no-load lifting speed is 10-30m/min, and the full-load lifting speed is 5-15m/min. The luffing speed is generally 0.1-0.5m/s, and the turning speed is generally 0.1-0.5r/min.
Mechanism design: The design of hoisting, luffing, and slewing mechanisms should meet the work requirements. For example, the safety factor of the wire rope of the hoisting mechanism is generally not less than 5-6, and the size deviation of the rope groove of drum is controlled within 0.5 mm. The speed adjustment range of the luffing mechanism should meet the actual operation requirements, and the luffing time is usually between 30 and 90 seconds. The design life of the slewing support of slewing mechanism is not less than 10000 hours.
Safety Design Standards
Protective devices: A variety of safety devices must be equipped, such as lifting height limiters, lifting weight limiters, anti-overturning devices, and windproof braking devices. When the lifting height limiter acts, the distance between the hook and the limit position should be not less than 0.5m; The accuracy of the lifting capacity limiter should reach 5%, when the lifting capacity exceeds 95% of the rated value, a early warning signal will be sent out, and when it exceeds 110%, the lifting power source will be automatically cut off; The windproof braking device shall be able to withstand the maximum wind force specified by the local authorities.
Electrical safety: The insulation resistance of electrical equipment shall not be lower than the specified value, the insulation resistance of the power circuit shall not be lower than 1MΩ, and the insulation resistance of the control circuit shall not be lower than 0.5MΩ. The grounding resistance should not be greater than 4Ω to ensure the safe operation of electrical equipment and prevent electric shock accidents.
Safety device configuration: There must be a travel limit for lifting, cart operation, and trolley operation. A switch that can cut off the main power supply of the engine room crane on the engine room platform shall be set. When not working, the engine room crane should have an anchoring device to prevent slipping.
Environmental Adaptability Standards
Temperature adaptability: It can work normally at the ambient temperature of -20℃-50℃. In low-temperature environments, heating and heat preservation measures should be taken to ensure the stability of hydraulic oil, lubricating oil, and other media; In high-temperature environments, there should be a good cooling device to ensure that the performance of all parts of the equipment will not be affected by overheating.
Anti-capsizing ability: The operation requirements of the ship under the conditions of heeling and pitching shall be considered, so as to ensure that the offshore crane can work normally under the conditions that the ship’s heeling is not more than 2 and the heeling is not more than 5.
Maintenance and Repair Standards
Maintainability design: It is necessary to consider the convenience of maintenance, including the design that is easy to overhaul, replace, and repair the marine crane, so as to quickly resume work when necessary. For example, key components should be easy to disassemble and install, and reasonable maintenance channels and platforms should be set up.
The universality of parts: Try to use standardized parts, reduce maintenance cost and difficulty, and improve the universality and interchangeability of parts.
